It is known to spin-dye polymers or copolymers of acrylonitrile with organic or inorganic colored pigments and to spin the spinning composition dyed in this way by the dry spinning or wet spinning process. However, the manufacture of the colored pigments used for this purpose requires a high outlay in respect of their finish in order to produce the necessary particle structure and particle fineness. In this connection it is not always possible to achieve a uniform and reproducible particle size distribution. When pigments are used in the spinning composition, however, inadequate particle size and particle size distribution lead to serious disadvantages; thus it is not possible to avoid continuous mechanical wear of the spinnerets and even clogging of the latter, which can lead to inaccuracies of denier or to the loss of individual spin filaments. In addition, depending on the fineness of their particles, colored pigments also cause more or less pronounced inhomogeneities within the spun filaments, which result in delustering effects, unfavorable influences on handle and impairment of the mechanical properties of the filaments, for example the tear strength. These disadvantages apply to both the dry spinning process and the wet spinning process.
It is also known to spin-dye polymers and copolymers of acrylonitrile by using dyestuffs which are soluble in the spinning solutions. Examples of such dyestuffs are complex compounds of basic dyestuffs with heteropoly acids, water-insoluble or sparingly soluble salts of aromatic sulfonic acids with basic dyestuffs or free non-quaternary dyestuff bases or salts thereof.
Complex compounds of basic dyestuffs with heteropolyacids are known, for example from French Patent Specification No. 1,068,382. However, these dyestuffs have the disadvantage that they only produce low depths of color, owing to the fact that they contain a very high proportion, in terms of weight, of the anion, which makes no chromophoric contribution, the ratio of dyestuff cation weight to anion weight being about 1 or less than 1. -Sulfonates of basic dyestuffs, which are manufactured by precipitating the basic dyestuffs from their aqueous solutions by means of aromatic sulfonic acids, are known, for example from German Patent Specification No. 1,077,372. In the known wet spinning processes, in which spinning is carried out from, for example, solutions of dimethylformamide, dimethylacetamide, dimethyl sulfoxide or ethylene carbonate or from aqueous thiocyanate solution, these dyestuffs lead to considerable bleeding in the aqueous coagulation, stretching and washing baths, and in dry spin-dyeing lead to bleeding in the aqueous stretching and washing baths, since the dyestuffs are not adequately fixed in the polymer. Here too, the ratio of dyestuff cation weight to anion weight is so low that it is not possible to achieve very deeply colored dyeings. -Free, non-quaternary dyestuff bases and salts thereof are known, for example from German Patent Specification No. 2,359,466 and German Auslegeschrift No. 2,411,328 or German Auselegeschrift No. 2,413,299. These dyestuffs are sparingly soluble or insoluble in water and therefore hardly bleed or do not bleed at all when the dyed spinning compositions are spun into water; in the dry spinning process there is likewise no staining of the downstream aqueous stretching and washing baths. However, the known spinning processes operated on a large industrial scale use a counter-current process, the aqueous medium passing through the different baths in the opposite direction to the spun filaments. The result of this is that, for example when using dimethylformamide as the solvent in the spinning composition, the coagulation bath of the wet spinning procedure contains about 30 to 70% by weight, the stretching bath contains about 15 to 70% by weight and the washing bath contains up to about 30% by weight, of dimethylformamide. However, since these dyestuffs or dyestuff salts are not adequately fixed in the polymer material, but are readily soluble in these baths, they also undergo considerable bleeding if these coagulation, stretching and washing baths are used, which also contain, as well as water, the fairly large quantities mentioned on the solvent used in the spinning composition.
Processes for spin-dyeing polymers and copolymers of acrylonitrile with dope-soluble dyestuffs, are also described in other publications, for example in German Patent Specification No. 1,044,022 and in the U.S. Pat. Nos. 3,148,935, 3,232,904, 3,673,182, 3,996,192, 4,020,037, 4,039,539, 4,100,131 and 3,770,727 as well as in the British Patent Specification No. 1,514,263. These dyestuffs are mainly compounds which also bleed considerably into the coagulation, stretching and washing baths in the wet spinning process.
The bleeding of the dyestuffs into these baths is, of course, not desirable and this disadvantage should, at least, be kept to the minimum proportions possible, since it has very adverse consequences in a variety of ways. Thus, for example, the quantity of dyestuff which has bled out is lost for spin-dyeing and poler color shades are produced that if non-bleeding dyestuffs with the same basic tinctorial strength are used. If mixtures of bleeding and non-bleeding dyestuffs are used at the same time in the spinning composition, the shade of the dyed filament is changed depending on the extent of the bleeding, so that a loss of color which varies with time and the degree of saturation of the baths in respect of the dyestuffs, can occur in the case of the dyed filaments. Furthermore, the coagulation, stretching and washing baths must be continuously regenerated in order to ensure constant spinning conditions; in addition, these baths must be worked up in respect of the solvents contained in them, and, in working up by distillation, the dyestuff which has bled out accumulates in the distillation sump, where it can undergo decomposition at the high temperatures which are required. The decomposition products can, however, cause contamination of the regenerated material and, if the latter is re-used, can have a harmful effect on the spinning process and the materials being spun. But even if the baths are regenerated by adsorption, for example through a bed composed of an acrylonitrile polymer or copolymer, with baths containing a great deal of dyestuff there is a rapid exhaustion of the capacity of the adsorbent.